The present invention relates to an apparatus and process for the electrical filtering of pressure measurements of the fluid pressure in a catheter.
The proliferation of intra-arterial pressure measurements and the associated technology has implied a greater degree of accuracy and confidence in the measurements than can often be realized. Among the multitude of considerations that are related to a catheter-manometer system, is that of frequency response. The addition of a rigid, fluid filled pressure transmission line, connecting the patient's arterial cannula or catheter to a pressure transducer will generally reduce the overall system frequency response. The formation of bubbles in the hydraulic system may introduce resonances at frequencies that will severely compromise the quality of the pressure waveform and the systolic values derived from it.
Despite careful attention by nursing and medical staff including frequent flushing, tightening of stopcocks and hardware, etc., inaccuracies introduced by the pressure system resonance are all too often present and remain to be dealt with.
In prior art apparatus, attempts have been made to address this problem with low pass filters that roll off the frequency response of the pressure amplifier at some frequency considered to be the lower limit of the unwanted resonance. Unfortunately, much theoretical and empirical evidence indicates that these resonances are very close to the primary frequency components of the waveform itself. In addition, as the hydraulic system ages, minute bubbles form that tend to shift the resonance to increasingly lower frequencies.